yucca (yŭkˈə) [key], any plant of the genus Yucca, stiff-leaved stemless or treelike succulents of the family Liliaceae (lily family), native chiefly to the tablelands of Mexico and the American Southwest but found also in the E United States and the West Indies. Yuccas in flower produce a large stalk of white or purplish blossoms. They are pollinated by the yucca moth, and in its absence they rarely fruit—a striking example of interdependence, since the moth, which lays its eggs during pollination and whose larvae feed on some of the developing seeds, cannot reproduce without the yucca. The leaves are usually stiff and spearlike, often with marginal threads. Several species are known as Adam's-needle, particularly those that are hardy and are cultivated in the North, most common of which is Y. filamentosa. The Joshua tree ( Y. brevifolia ) is a picturesque treelike species of desert regions. Mormons crossing the California deserts are said to have so named it because the grotesquely angular branches looked like the outstretched arms of a Joshua leading them out of the wilderness. The Spanish bayonet ( Y. aloifolia ) is another that is treelike in form, and the Spanish dagger ( Y. gloriosa ) is stemless or has a short trunk. The fruits and sometimes the flowers of several species of yucca were used as food by Native Americans. Certain species, particularly Y. baccata and Y. glauca, are called soap plant because of the use of their roots for soap. The fibers of some kinds have been utilized. A yucca is the state flower of New Mexico. Yuccas are classified in the division Magnoliophyta, class Liliopsida, order Liliales, family Liliaceae.